Catheters in the form of flexible tubes of a length to be inserted through a natural or incised opening in the body for introduction of fluids into the body or for drainage of fluids from the body are well known. Most such tubes are held in place by adhesive tape or its equivalent. However, since the tube is generally comprised of rubber or plastic, the tape does not always adhere securely and, further, since it is exposed to abrasive contact of clothing and/or bedding, it can be loosened by a restless patient. Without some means of securing the tube in place, there is always the risk that the patient, willingly or unwillingly, or some other person, may pull the tube out with serious consequences. It is the purpose of this invention to provide an improved catheter as, for example, a T tube structured to prevent inadvertent or purposeful withdrawal of the tube.